A rapid cold hardening (RCH) and supercooling capacity usually play crucial roles in survival during the overwintering period in the tobacco budworm, Helicoverpa assulta, a freeze-susceptible species. Cryoprotectants such as polyol or sugar affect RCH and maintain fluid status of hemolymph. This study is performed to identify cryoprotectants as a RCH factor in H. assulta. Pre-exposure of H. assulta larvae to 4℃ significantly increased survival at -10℃ in all developmental stages from egg to adult. RCH was dependent on the duration of the pre-exposure period. RCH also significantly enhanced the supercooling capacity. Analysis of cryoprotectants from the hemolymph revealed that the pre-exposure treatment allowed the larvae to accumulate glycerol and trehalose among polyols examined. In addition, unknown materials from 2 peaks were also increased. TIC analysis revealed 3 predicted formulas for unknown materials, C26H24O20S or C3H4N6OS and C22H20O21. Glycerol-3-phosphate dehydrogenase (GPDH) and glycerol 3-phosphatase (G3P) that involving in glycerol biosynthesis were identified from the transcriptome of H. assulta 4th instar larvae. Based on the expression level of transcripts, the expressions of GPDH and G3P were relatively increased when compared to that of the control, suggesting that these genes contribute to overwintering and biosynthesis of glycerol.

• Wook Hyun Cha(Department of Biology, Kyungsung University)
• Yoon Jung Hwang(Department of Biology, Kyungsung University)
• Dae-Weon Lee(Department of Biology, Kyungsung University)